When Thomas Keller tells you to eat raw tuna membrane, you do it. Small matter that the sticky, silver stuff between the fleshy parts of the fish looks like saliva dripping from a knife.

After all, Keller is the famed chef behind The French Laundry, a Michelin three-star restaurant in Napa Valley, and you're helping him write his first cookbook. And to be fair, you're the one who asked why he's removing it to prepare tuna tartare.

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So Michael Ruhlman did as he was told and picked up his first lesson for "The French Laundry Cookbook" the hard way: Sometimes you have to experience the really bad in order to avoid it.

Such are the hazards of being a cookbook co-author or ghostwriter. It's not all caviar and cupcakes for those who assist today's busy chefs in translating their singular visions into usable step-by-step guides for home cooks.

Like culinary method actors, these writers do whatever it takes to crawl into a chef's head — or at least under their toque — to find, not just their voice, but their ethos. At the same time, some are charged with the equally challenging task of ensuring that the recipes being adapted to a consumer kitchen don't turn out half-baked.

Ruhlman threw himself into the job, living with Keller for five weeks as he worked on "The French Laundry Cookbook." A former New York Times copyboy who wrote "The Making of a Chef" based on his experience at the Culinary Institute of America, he brought a cook's knowledge and a journalist's approach to the project.

"I reported that cookbook," says Ruhlman, of suburban Cleveland. "I hung out in the kitchen. I interviewed chefs. I interviewed purveyors. I observed. I asked questions. I stayed up late with Thomas after service and we talked.

"By the end of my time there, when he would say, 'Why did I add honey to the mascarpone cheese to garnish the lemon tart?' I knew the answer."

The two have continued to collaborate with others to produce cookbooks, most recently with "Bouchon Bakery," which came out in October. Ruhlman says he wrote every word in it, minus the step-by-step recipes, channeling three other voices: Keller, the head baker and the executive pastry chef. The process proved the precept that face time matters.

"A writer's got to be a good mimic," Ruhlman says." "You work with a chef long enough, you start to do impressions of the chef."

Alcohol helps too. One of the most productive nights that former "Top Chef" contestant Kevin Gillespie had working on his recently released cookbook, "Fire in My Belly," didn't come in the kitchen of the Woodfire Grill in Atlanta, where he is executive chef, or sitting at home on a couch across from co-author David Joachim. Instead, it came in a grimy New York City bar after a night of cooking.

"I had a few drinks in me, and I guess I just went off on a tear. I was like: I am ready to talk about my philosophy on food as it relates to everything in the world," Gillespie recalls. "(Joachim) thankfully was sober enough that he pulled out the laptop computer and just started writing. … A lot of that made it in the book."

These spontaneous yet intimate conversations are a treasure trove for writers, showing how a chef talks, the idiosyncratic phrases they use, and the pacing of the stories they tell.

"The best details come when they are completely relaxed and they don't care what the home cook needs or wants to hear," says Joachim, a former cookbook editor at Rodale Books who lives outside of Philadelphia. "Part of my job is making them feel relaxed."

That's essential because today's cookbooks are about much more than the recipes they contain. Instead, many focus on the stories behind dishes and the chef's personal saga.

"I wanted to make sure that we had somebody who could tell a good story because for me the stories are really important," says Keller. "I wanted to make sure that the cookbook had another dimension to it."

Sometimes, though, things get lost in translation. Gillespie says that the first time he saw any of the writing for the book, "it did and it didn't" sound like him. So he says he told Joachim: "I want you to write this closer to the words that I'm saying, closer to the way I'm saying it to you, even if that means that there are times that we say something that's a bit crass or maybe something that isn't the most eloquently described."

When a partnership is successful, the reader should never feel as if they are not hearing from the chef directly, Joachim says.

"If I've done my job properly … readers feel like they're in the kitchen with the chef," he says. "Often that's a matter of me getting out of the way."

A natural question might be why a celebrity chef would seek out this kind of help in the first place. Why find a Cyrano to feed you your own lines?

"Working 12 to 14 hours a day, six days a week, and trying to write a book at the same time? It's a little questionable," Keller says. "I'm also a person that realized the things I'm good at and the things I'm not good at. … And I don't know how to write cookbooks."

Or as Ruhlman puts it: "Chefs need somebody to articulate what they can't. ... Cooks are cooks because they're physical people, not because they're verbal people."

Gillespie says that while he was confident in his ability to tell his tale, he wanted guidance from someone who had done such a project before, knew what to focus on, and could offer a strong writing background.

"I felt like people probably didn't want to read a ton of my run-on sentences," he says.

The idea was to find a true partner, not a hired gun who would simply write his book for him. That's when he found Joachim, a former college English teacher who is now starting his 40th cookbook and happens to share the chef's agent. The seeds of many such relationships often begin with agents, editors or simple word of mouth.

Jeff Michaud, executive chef and co-owner of several restaurants, including Osteria in Philadelphia, chose to partner with Joachim on an upcoming book, tentatively titled "Eating Italy," based on the positive experience his business partner, Marc Vetri, had with the writer.

While Michaud knew he didn't have the writing skills to produce a proper cookbook on his own, he did make notes and write down the stories to serve as the book's foundation.

It's a partnership to which the writer has something valuable to add: perspective. Whether in the organization of the book or in the explanation of a dish, they may see what the chef takes for granted — that a home cook, for example, may not be familiar with the proper method for glazing carrots, how to locate bone-in venison chops, or even what the term "julienne" means.

Rick Rodgers has worked behind the scenes on more than 30 cookbooks, but he still recalls the time he made chocolate mousse with ground coffee beans because the recipe didn't specifically call for brewed coffee.

"Whenever I do a project, I always go back to the days when I was learning how to cook out of the books of people like Julia Child and Marcella Hazan … and how clear their recipes were and the questions that I had in my mind," he says.

Many busy chefs don't have time to take the dishes they create and translate them from basic formulas — often scribbled down with only the briefest of instructions for highly trained line cooks — into a set of replicable instructions for consumers. That's where Rodgers comes in. He tests and tweaks in his New Jersey home kitchen, making sure that none of the differences between a restaurant environment and a domestic one get in the way.

"For a chef's book, I want to buy the ingredients at a consumer level, not at the wholesale level, to be sure that the home cook can recreate the recipe," he says.

That's the easy part, says Rodgers, who has developed cookbooks from drafts that he was given by the likes of Chicago chef Art Smith and, most recently, "Real Housewives of New Jersey" star Teresa Giudice. Rodgers, who edited "The Essential James Beard Cookbook," which was just released, says that some conversions are almost impossible to quantify.

"I'm watching the chef cook the food at the restaurant, and he's using literally a pinch of this and a spoonful of that and a handful of that. So then I have to estimate, watching him. I write down my notes, then we have to go into the kitchen with a measuring spoon and a scale and start all over again," he says. "If you have to multiply that process times 100 or 150, there is a lot of opportunity for human error."

There's a bit of magic in what these chefs do that's tough to replicate. While working on 2011's "Rustic Italian Food," Joachim remembers watching Philadelphia chef Vetri, who has several Philadelphia restaurants including Vetri and Osteria, extrude pasta using only two ingredients, semolina and water. That might have been a piece of cake to describe if only the amount of water had mattered. More important to Vetri was the texture, according to the writer.

"I asked him to describe it: How do you know how much to add? … He said, 'It should feel like damp sand.' That's a great description. So that's right from his mouth, and I just wrote that into the recipe."

Mary Goodbody, founding editor of Cook's Magazine (now Cook's Illustrated) has facilitated scores of cookbooks, inhabiting other people's voices to write innumerable headnotes, introductions and sidebars. She says there's no ego in this work, and she's fine with that.

"I leave any pride of authorship on the doorstep, except for things about grammar. If the chef doesn't like the way something sounds, that's fine. … I will just change it because this is their book and I want them to be happy," she says. "I used to say, sort of cavalierly, that 'I don't care if my name's on the book. I just want my name on the check.'"

While the Connecticut writer's name has appeared on the cover of numerous books — as it does in "If It Makes You Healthy" by Sheryl Crow and Chuck White — just as often chefs wait until the acknowledgments page to praise her contributions.

Of course, that raises the question: Who writes those? Goodbody answers with a hearty laugh.

"I do have clients who have asked me to," she says. "That's hard, you know?"